Үү and Өө are sometimes also written as the Ukrainian lettersЇї (or Vv) and Єє respectively,[5] when using Russian software or keyboards that do not support them.

Initial long vowels and non-initial full vowels are written with double vowel letters, while initial short vowels and non-initial epenthetic vowels are written with single vowel letters. Conversely, every vowel letter except у and ү can also represent schwa and zero in non-first syllables. Palatalisation is indicated by и (i), the soft sign ь (') or е (ye), ё (yo), я (ya) and ю (yu) after the palatalised consonant. These latter letters are pronounced without [j] in that position. Щ is never used in Mongolian and only used in Russian words containing the letter.[6] It is pronounced identically to Ш, and is often omitted when teaching the Cyrillic alphabet. Sometimes, Russian loanwords with Щ will be spelled with Ш instead: борш, Хрушев. The difference between [e~i] might be dialectal,[7] while the difference between ɵ~o is positional.[8]

/ɡ/ and /ɢ/ are both indicated by the letter г ⟨g⟩, but the phonetic value of that letter is mostly predictable. In words with "front" (+ATR) vowels (see Mongolian phonology for details), it always means /ɡ/, because only /ɡ/ occurs in such words. In words with "back" (−ATR) vowels, it always means /ɢ/, except syllable-finally, where it means /ɡ/; to acquire the value of /ɢ/, it is written as followed by a single mute syllable-final vowel letter. Similarly, a mute vowel is added to final н ⟨n⟩ to make it denote /n/ and not /ŋ/. ф (f) and к (k) are loan consonants and will often be adapted into the Mongolian sound system as [pʰ] and [x].[6]

The original plan as at 10 October 1945 was to use э only at the beginning of words and in long vowel combinations (as is done in other languages written using Russian-based Cyrillic), дз for modern з, дж for modern ж, ии for modern ий and йо for modern е (to represent the "yö" sound at the beginning of words), but the alphabet was changed to its final form on 13 November.[9]